Keith Allington joined in July 2010 as managing director of United House Limited to spearhead new build construction, refurbishment and community regeneration operations.
Allington joined from Ardmore where he spent 20 years and rose through the ranks to become a main board director.
Industry sources said Allington left suddenly in a surprise move.
A United House statement said: “We can confirm that Keith Allington has left the company.
“Colin Forrest has been appointed, on an interim basis, as MD of United House Limited.
“Colin has more than 30 years experience in the construction sector, including eight years as Chief Executive of The Pearce Group (part of ISG plc).”